ARH headers and CORSA extreme installed

JJ f150harley said:

Hahahaha. Dam a diesel with a stack is on my list of future trucks.

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Cant say i don't miss it!

Dam she's sick. Man that must have been a tough choice to get rid of her. That 6.5 bed came in handy compared to our little 5.5 beds.

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JJ f150harley said:

Dam she's sick. Man that must have been a tough choice to get rid of her. That 6.5 bed came in handy compared to our little 5.5 beds.

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Ahh it wasn't tough at the time but now I miss her dearly haha. I gotta say the raptors nimbleness it a fresh breath of air compared to that hog tho

Hahaha yea that's for sure. That's a rig and its certainly different than these. Ive only had f150s and this is a step up compared to my 99. So this handles like a dream compared to it and urs I'm sure.

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BRAPPPP said:

Thanks man. I'll do that. Did yours have the gargle/sounding like its gonna die at idle issues? It might be just the non cat guys with that issue.

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No never had that

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Just want to chime in here a bit, you should probably add converters to your setup. Modern cars with all this fuel injection technology really like converters, they help clean up excess exhaust gasses and add a tiny amount of back pressure allowing the truck to be a bit more responsive.

Stainless Works said:

Just want to chime in here a bit, you should probably add converters to your setup. Modern cars with all this fuel injection technology really like converters, they help clean up excess exhaust gasses and add a tiny amount of back pressure allowing the truck to be a bit more responsive.

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SW so the truck will be more responsive if we do cats? Will it hurt it much in the long run if running no cats?

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Stainless Works said:

Just want to chime in here a bit, you should probably add converters to your setup. Modern cars with all this fuel injection technology really like converters, they help clean up excess exhaust gasses and add a tiny amount of back pressure allowing the truck to be a bit more responsive.

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Then wouldn't we also be better off running 3/4 for the back pressure as well ?

Back pressure is not the issue, in fact it shouldn't even be brought into the conversation because "back pressure" just means restriction on a modern engine. Placing a muffler or added restriction is not going to necessarily help with low end torque.

Increasing exhaust gas velocity at low RPMs will help with low end torque. One way to increase exhaust gas velocity at lower RPMs is long tube install headers with smaller primary tubes. However, those smaller primary tubes can create a relative restriction at high RPMs because there isn't enough real estate for the gas to flow through uninhibited. You might call that "back pressure", but it's really just a restriction and robs max horsepower gains. None of this is true, however, if the headers are simply too larger or too small for the application.

If they are too large, the exhaust gasses will move too slowly at low RPMs. Think of a small garden hose vs. a large garden hose. Assume they are both capable of allowing the same volume of water to flow out of them when the faucet is on half way, the smaller diameter garden hose will result in the water flowing faster, right? But, when you crank up the amount of water flowing through the hose, there comes a point where the smaller diameter hose cannot allow as much volume of water to flow out as the larger hose.

With that in mind, it brings us to exhaust scavenging. Exhaust gasses are a moving mass. What happens behind a moving mass? A low pressure area develops. Just like drafting in Nascar. The lead car literally pulls the car along behind it. Maybe some of you have experienced this on the highway when behind a semi truck.

So, exhaust scavenging is what we need to talk about. Increasing exhaust gas velocity will facilitate a faster and more complete emptying of the combustion chamber before the exhaust valve(s) slam shut. Why? Because the process of faster exhaust gas velocity will create a lower pressure area behind each pulse, which will "suck" all the remaining exhaust gasses out. If you're able to get those exhaust gasses all cleared out, each cylinder can then use more available volume for oxygen and gas to fill it up. More oxygen, more gas? More power. Simple.

However, as the RPMs climb, the exhaust pulses from each cylinder bank occur closer together, and thus there will be more exhaust gas trying to occupy a smaller volume of space. When that happens, the traffic jam occurs and exhaust gas velocity slows again. If your primary tubes are on the smaller side of what's appropriate for your engine, the torque curve will be more evident down low. However, that traffic jam at higher RPMs starts working against you.

On the other hand, the larger diameter primary tubes (in this case 1 7/8") will likely move the torque curve a little higher in the RPM range, but will allow for free flow and maximum exhaust gas velocity at high RPMs. More top end excitement and max horsepower.

Removing the cats complicates things further. Modern cats are pretty darn free-flowing. They should not, unless they're clogged, create any restriction until maybe very high RPMs. Even at that, the exhaust gasses are so hot that they enter the cats, and accelerate upon leaving them. More importantly, the O2 sensors are sending very important information to your engine's PCM in regards to air-to-fuel ratio. Not only are they important for emissions, but your engine simply will not gain the information necessary to run 100% correctly all of the time. The tune can play a major role on what's going on here. I'd recommend visiting a local shop to have a dyno tune and/or street tune performed so your truck can be DIALED the way YOU want it. Believe me, there's a lot that can be done in person vs. a mail order tune. Hope this helps.

GotExhaust.com said:

Back pressure is not the issue, in fact it shouldn't even be brought into the conversation because "back pressure" just means restriction on a modern engine. Placing a muffler or added restriction is not going to necessarily help with low end torque.

Increasing exhaust gas velocity at low RPMs will help with low end torque. One way to increase exhaust gas velocity at lower RPMs is long tube install headers with smaller primary tubes. However, those smaller primary tubes can create a relative restriction at high RPMs because there isn't enough real estate for the gas to flow through uninhibited. You might call that "back pressure", but it's really just a restriction and robs max horsepower gains. None of this is true, however, if the headers are simply too larger or too small for the application.

If they are too large, the exhaust gasses will move too slowly at low RPMs. Think of a small garden hose vs. a large garden hose. Assuming they are both capable of allowing the same amount of water to flow out of them, the smaller diameter garden hose will result in the water flowing faster, right? But, when you crank up the amount of water flowing through the hose, there comes a point where the smaller diameter hose cannot allow as much volume of water to flow out as the larger hose.

With that in mind, it brings us to exhaust scavenging. Exhaust gasses are a moving mass. What happens behind a moving mass? A low pressure area develops. Just like drafting in Nascar. The lead car literally pulls the car along behind it. Maybe some of you have experienced this on the highway when behind a semi truck.

So, exhaust scavenging is what we need to talk about. Increasing exhaust gas velocity will facilitate a faster and more complete emptying of the combustion chamber before the exhaust valve(s) slam shut. Why? Because the process of faster exhaust gas velocity will create a lower pressure area behind each pulse, which will "suck" all the remaining exhaust gasses out. If you're able to get those exhaust gasses all cleared out, each cylinder can then use more available volume for oxygen and gas to fill it up. More oxygen, more gas? More power. Simple.

However, as the RPMs climb, the exhaust pulses from each cylinder bank occur closer together, and thus there will be more exhaust gas trying to occupy a smaller volume of space. When that happens, the traffic jam occurs and exhaust gas velocity slows again. If your primary tubes are on the smaller side of what's appropriate for your engine, the torque curve will be more evident down low. However, that traffic jam at higher RPMs starts working against you.

On the other hand, the larger diameter primary tubes (in this case 1 7/8") will likely move the torque curve a little higher in the RPM range, but will allow for free flow and maximum exhaust gas velocity at high RPMs. More top end excitement and max horsepower.

Removing the cats complicates things further. Modern cats are pretty darn free-flowing. They should not, unless they're clogged, create any restriction until maybe very high RPMs. Even at that, the exhaust gasses are so hot that they enter the cats, and accelerate upon leaving them. More importantly, the O2 sensors are sending very important information to your engine's PCM in regards to air-to-fuel ratio. Not only are they important for emissions, but your engine simply will not gain the information necessary to run 100% correctly all of the time. The tune can play a major role on what's going on here. I'd recommend visiting a local shop to have a dyno tune and/or street tune performed so your truck can be DIALED the way YOU want it. Believe me, there's a lot that can be done in person vs. a mail order tune. Hope this helps.

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Thank you. I think the issue is a combination of no cats And the tune. I really enjoyed that low end torque and didn't know that I would actually lose low end torque from the stock manifolds only that it would not improve as much as the 3/4 primary.